Constant Power Load

Constant power load for DC or AC supply

Since R2020a

• 

Libraries:
Simscape / Electrical / Passive

Description

The Constant Power Load block implements a constant power load for a DC or AC supply.

If you set the Load type parameter to DC:

• The block outputs a nominal rated power as long as the voltage from the DC supply is equal to or greater than the value specified for the Minimum supply voltage parameter.

• When the voltage from the DC supply drops below the Minimum supply voltage, the load behaviour changes and the block acts as a constant resistance. If the supply voltage becomes negative, the block acts as a constant reverse conductance.

To ensure smooth transitions between these behaviours, the block uses a third-order polynomial spline with continuous derivatives. You can specify the width of this transition using the Transition voltage width parameter.

If you set the Load type parameter to AC:

• The block outputs a nominal rated power as long as the voltage from the AC supply is equal to or greater than the value specified for the Minimum supply voltage (RMS) parameter.

• When the voltage from the AC supply drops below the Minimum supply voltage (RMS), the load behaviour changes and the block models a load with constant impedance.

For more information about the equations for the AC load type in a three-phase system, see the Equations section of the Constant Power Load (Three-Phase) block.

Faults

The Constant Power Load block allows you to model an electrical fault as an open circuit. The block can trigger fault events at a specific time.

You can also choose whether to issue an assertion when a fault occurs, by using the Reporting when a fault occurs parameter. The assertion can take the form of a warning or an error. By default, the block does not issue an assertion.

Load-Flow Analysis

If the block is in a network that is compatible with the frequency-time simulation mode, you can perform a load-flow analysis on the network. A load-flow analysis provides steady-state values that you can use to initialize a machine.

For more information, see Perform a Load-Flow Analysis Using Simscape Electrical and Frequency and Time Simulation Mode.

Ports

Conserving

+ — Positive terminal

electrical

Electrical conserving port associated with the constant power load positive terminal.

- — Negative terminal

electrical

Electrical conserving port associated with the constant power load negative terminal.

Parameters

Main

Load type — Load type

DC (default) | AC

Type of load. Select DC to use this load with a DC supply or AC to use this load with an AC supply.

Power consumed — Power consumed

100 W (default) | scalar

Nominal power consumed by the block.

Dependencies

To enable this parameter, set Load Type to DC.

Minimum supply voltage — Minimum DC supply voltage

20 V (default) | scalar

Minimum voltage the DC supply needs to give the block to act as a constant power load.

Dependencies

To enable this parameter, set Load Type to DC.

Reverse conductance — Reverse conductance

1e-6 S (default) | scalar

Value of the reverse conductance when the supply voltage becomes negative.

Dependencies

To enable this parameter, set Load Type to DC.

Transition voltage width — Transition voltage width

1e-3 V (default) | scalar

Transition voltage width used to ensure smooth transitions between the block's behaviours when the supply voltage drops below the Minimum supply voltage or becomes negative.

Dependencies

To enable this parameter, set Load Type to DC.

Active power consumed — Active power consumed

500 W (default) | scalar

Active power consumed by the block.

Dependencies

To enable this parameter, set Load Type to AC.

Reactive power consumed — Reactive power consumed

0 V*A (default) | scalar

Reactive power consumed by the block.

Dependencies

To enable this parameter, set Load Type to AC.

Rated frequency — Rated frequency

60 Hz (default) | scalar

Rated frequency.

Dependencies

To enable this parameter, set Load Type to AC.

Minimum supply voltage (RMS) — Minimum AC supply voltage

200 V (default) | scalar

Minimum voltage, in RMS, the AC supply needs to give the block to act as a constant power load.

Dependencies

To enable this parameter, set Load Type to AC.

Faults

Enable open circuit fault — Whether to enable faults modeling

Off (default) | On

Select On to enable faults modeling and expose the associated parameters in the Faults section to select the reporting method and specify the time at which the fault triggers.

Reporting when a fault occurs — Whether to issue an assertion when a fault occurs

None (default) | Warn | Error

Choose whether to issue an assertion when a fault occurs:

• None — The block does not issue an assertion.

• Warn — The block issues a warning.

• Error — Simulation stops with an error.

Dependencies

To enable this parameter, set Enable open circuit fault to On.

Simulation time for fault event — Time before entering faulted state

1 s (default) | scalar

Simulation time when the block enters the faulted state.

Dependencies

To enable this parameter, set Enable open circuit fault to On.

Open-circuit conductance — Open-circuit conductance

1e-4 S (default) | scalar

Conductance during the open-circuit state.

Dependencies

To enable this parameter, set Enable open circuit fault to On.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2020a